Indigo carmine
| Indigo carmine | |
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3,3'-dioxo-2,2'-bis-indolyden-5,5'-disulfonic acid disodium salt |
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Other names
indigotine; 5,5'-indigodisulfonic acid sodium salt |
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| Identifiers | |
| CAS number | 860-22-0  |
| PubChem | 5284351 |
| ChemSpider | 4447431 |
| UNII | D3741U8K7L |
| ATC code | V04 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C16H8N2Na2O8S2 |
| Molar mass | 466.36 |
| Appearance | purple solid |
| Melting point |
>300 °C |
| Solubility in water | 10 g/L (25 °C) |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Indigo carmine, or 5,5'-indigodisulfonic acid sodium salt, also known as indigotine or FD&C Blue #2 is a pH indicator with the chemical formula C16H8N2Na2O8S2. It is approved for use as a food colorant in the United States[1] and the EU[2] and has the E number E132.
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[edit] Uses
| Indigo Carmine (pH indicator) | ||
| below pH 11.4 | above pH 13.0 | |
| 11.4 | ↔ | 13.0 |
The primary use of Indigo carmine is as a pH indicator. It is blue at pH 11.4 and yellow at 13.0. Indigo carmine is also a redox indicator, turning yellow upon reduction. Another use is as a dissolved ozone indicator[3] through the conversion to isatin-5-sulfonic acid[3]. This reaction has been shown not to be specific to ozone, however: it also detects superoxide, an important distinction in cell physiology.[4]. It is also used as a dye in the manufacturing of capsules, and in obstetrics, Indigo carmine-based dye is used to detect amniotic fluid leaks.
[edit] Health concerns
Indigo carmine is harmful to the respiratory tract if inhaled. It is also an irritant to the skin and eyes. Proper laboratory cautions (lab coat, gloves, goggles) are advised.
[edit] See also
[edit] References
- ^ Summary of Color Additives for Use in United States in Foods, Drugs, Cosmetics, and Medical Devices, United States Food and Drug Administration
- ^ Current EU approved additives and their E Numbers, Food Standards Agency, 26 November 2010
- ^ a b Takeuchi K, Ibusuki T (March 1989). "Quantitative determination of aqueous-phase ozone by chemiluminescence using indigo-5,5'-disulfonate". Anal. Chem. 61 (6): 619–23. doi:10.1021/ac00181a025. PMID 2729594.
- ^ Kettle AJ, Clark BM, Winterbourn CC (April 2004). "Superoxide converts indigo carmine to isatin sulfonic acid: implications for the hypothesis that neutrophils produce ozone". J. Biol. Chem. 279 (18): 18521–5. doi:10.1074/jbc.M400334200. PMID 14978029.
